Emerald and Diamond Ring. Owing their fabled rich green to the element chromium, emeralds have been one of the most highly prized stones for millennia. Emeralds are seldom completely free from inclusions, and are almost always enhanced with oil (traditionally, cedar oil) to help with their transparency. This emerald, with its classic shade of green, and very good clarity (though still with a trademark ‘jardin’ of natural inclusions), is a beautiful example of this famous stone, a lush green stone is a great choice for an engagement ring.